Electric and hybrid vehicles typically include an alternating current (AC) electric motor which is driven by a DC power source, such as a high voltage storage battery which can run, for example, at 250 V DC. The AC electric motor runs on an alternating current. Motor windings of the AC electric motor can be coupled to inverter module(s) by an AC interconnection system which includes an AC bus bar for carrying the alternating current.
The inverter module is a power supply which converts the DC power from the battery to AC power which drives or runs the AC electric motor. A stator of the AC electric motor includes a number (e.g., three) of motor windings. The alternating current goes into the motor windings and powers the AC electric motor. A connector connects the AC motor to the inverter. The bus bar can be made of copper.
Each inverter module can include a current sensor or sensors which are coupled to the bus bars. The current sensors measure the alternating current generated by the inverter, and feed the measurements back to a controller which monitors the alternating current.
FIG. 1 is a schematic diagram of a conventional electric motor system. The conventional electric motor system includes an inverter module 20, a bus bar 18, an intermediate bus bar 17, a motor winding 16, and an electric motor 10. The inverter module 20 is coupled to the bus bar 18 which is coupled to the intermediate bus bar 17 which is coupled to the motor winding 16 which is part of the electric motor 10. The inverter module 20 sends an alternating current to the bus bar 18. The bus bar 18 sends the alternating current to the intermediate bus bar 17. The bus bar 18 has an AC current sensor assembly 12 coupled to the bus bar 18 which senses or measures the alternating current. The intermediate bus bar 17 sends the alternating current to the motor winding 16 where it drives or runs the electric motor 10.
The recent popularity of hybrid electric cars has increased the use of high density power electronics in an “under the hood” environment where temperatures in the engine compartment can often reach 125 C. or more. Due to the high temperatures in such environments, it has become particularly important to provide techniques for dealing with the effects of high temperatures on the power electronics used in such environments.
Unfortunately, the system of FIG. 1 requires the use of fasteners between the motor windings 16 and the intermediate bus bar 17 and between the intermediate bus bar 17 and the bus bars 18 which can increase the cost of the interconnection system. Moreover, these fasteners have resistances associated therewith which can undesirably introduce electrical noise. In addition, crimping of the intermediate bus bar 17 can also be problematic.
In addition, in some cases the AC current sensor assemblies 12 used to sense current traveling along the bus bar 18 can be susceptible to failure when used in high current and/or high temperature environments. For example, off the shelf current sensors may be rated, for instance, to a maximum operating temperature of 105 C. To deal with these high temperatures, vehicle manufacturers have been forced to use custom current sensors which are designed and rated for high temperature applications or environments and can withstand the operating temperatures in such environments. However, these current sensors are relatively expensive, and it would be desirable to provide techniques which can allow cheaper or lower rated current sensors to be used in an under the hood environment.
Notwithstanding these advances, there is a need for high current/power AC interconnection systems which can be used, for example, to connect a motor to an inverter. It would be desirable to reduce the cost and size of such interconnection systems. It would also be desirable to reduce and possibly eliminate the number of interconnections needed between components of the interconnection system to reduce EMI noise. There is also a need for a high current, low noise AC interconnection system which can be used, for example, to connect an integrated dual wound motor to a dual inverter. It would also be desirable to use cheaper, off-the-shelf current sensors despite the high temperature operating conditions. Other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.